Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

Cream together the cold unsalted butter and granulated sugar using an electric mixer for about 3-5 minutes.

Add the large egg and blend until fully incorporated for about 1 minute.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt.

Gradually mix the dry ingredients into the butter-sugar mixture until just combined.

Divide the dough into 3-4 portions and knead in your chosen Jello powder until incorporated.

Wrap the dough portions in plastic wrap and refrigerate for about 15-20 minutes.

Form balls of dough about 1 inch in diameter, coat them in additional sugar, and flatten slightly before placing on baking sheets.

Bake for 8-10 minutes, until edges are set, then allow to cool on sheets for 2 minutes before transferring to a wire rack.

Enjoy your colorful Jello Sugar Cookies once cooled!